We have developed a new device for guiding invasive procedures called the sonic flashlight (SF), which merges an ultrasound image with a direct view of the patient by means of a half- silvered mirror. The hand-held device permits insertion of needles directly into a virtual image of the ultrasound scan, which floats beneath the skin showing the underlying anatomy in real time. After a number of years of NIH-funded development we have recently tested the SF successfully in patients for placement of peripherally inserted central catheter (PICC) lines. Trials for jugular line placement and breast biopsy are being planned. The depth to which the sonic flashlight is practical is limited as a hand-held device, since the mirror requires a real display of equal size to the virtual image. Thus certain ultrasound-guided procedures such as liver biopsy and amniocentesis are not practical with the SF, because attaching such a large display would make a hand-held transducer unwieldy. We now propose replacing the half- silvered mirror with a transparent holographic plate to construct a holographic sonic flashlight (HSF). The new version of the SF will produce larger images with more varied shapes, expanding the range of procedures that may be guided to include those involving deeper structures within the patient without the increased size and weight that would be required of a corresponding mirror-based SF. In particular our aims are as follows: (1) Design, construct, and calibrate the first HSF, (2) Evaluate human performance operating the HSF, using custom phantoms for clinical procedures deeper than practical with the original SF, including liver biopsy and amniocentesis, and (3) Develop a registration system for displaying the equivalent slice of pre-acquired computerized tomography (CT) data for the liver. We plan to submit a follow-on proposal for multi-center clinical trials during the third year of the grant for liver biopsy and amniocentesis. By extending the mirror-based sonic flashlight to holography and displaying registered CT data, we will have expanded the realm in which a fundamentally new way of displaying medical data may be used, to include deeper invasive procedures within the patient and other imaging modalities in addition to ultrasound. (Relevance) We have developed a device called the sonic flashlight, which uses a half-silvered mirror to reflect the ultrasound image in such a way that the image appears to float within the patient at its correct location, so that a needle can be guided to targets beneath the skin by inserting it directly into the image. We now propose replacing the half-silvered mirror with a holographic plate to produce a holographic sonic flashlight capable of larger and more versatile images, expanding the types of procedures that may be guided to include those involving deeper structures within the patient. We also propose making the device capable of displaying a slice of pre-acquired CT data in its proper location.